Zeolite-containing catalysts are commonly used in the petroleum refining industry. A significant area of application is in hydrocracking processes which convert certain low grade distillates and oils to valuable transportation fuels, particularly, high octane gasoline, diesel fuel and premium quality jet fuel.
A particular class of zeolite catalysts which are of special interest in hydrocracking processes are those which use Y-type zeolites in combination with an inorganic oxide component which serves as a binder for the zeolite component. The zeolite/inorganic oxide catalyst is prepared by various processes into particles or pellets which are suitable for use in a fixed bed hydrocracking process.
Examples of such zeolite-containing catalysts, their preparation and their use in hydrocracking processes are disclosed in U.S. Pat. No. 4,401,556 to Bezman, et al.; U.S. Pat. No. 3,449,070 to McDaniel, et al.; U.S. Pat. No. 4,252,688 to Gallei, et al.; U.S. Pat. No. 4,419,271 to Ward; U.S. Pat. No. 4,429,053; to Ward, U.S. Pat. No. 4,456,693 to Welsh; and U.S. Pat. No. 4,556,646 to Bezman, the disclosures of which patents are incorporated herein by reference.
Hydrocracking is a very versatile process and is critically important to the economics and operation of petroleum refining. In the continually changing refining business environment, hydrocracking processes and consequently the catalysts used therein must also change to meet technical and economic requirements. The changing requirements placed on the hydrocracking processes result from declining feed stock quality, changing product demand patterns, increasingly stringent product quality requirements imposed by industry and government regulations as well as the ever present desire to increase unit throughput with minimum capital investment. Therefore, it is an object of this invention to maintain efficient conversion of low grade distillates and gas oils while increasing the selectivity for production of liquid products and decreasing the yield of light gases. It is a further object of this invention to accomplish the increased liquid selectivity without any decrease in catalyst activity or increase in coke formation.